The light armed cohorts discussion and evidence

[aquilifer]

Maybe a stupid question, but why didn't the romans equip their light auxilia skirmishers with pila instead of javelins?

I mean, from what little I know, the pila is better at piercing armour/shields right?

Is it that javelins are easier to produce? (probably also cheaper since I have read once that pila take longer to produce since it has the shaft inside and stuff)

Or do javelins on average just have better momentum or range (maybe even lighter then a pilum?) since speed and keeping distance is more important for skirmishers, since their job is to harass and pepper the enemy before the heavier infantry charge in ...